The effects of electromagnetic interference (EMI) have significant impact on a wide variety of electrical and electronic systems that are used in everyday life, as well as in military and space exploration applications and activities. In particular, EMI, together with electro-migration and electrostatic discharge, can impact the safe and reliable operation of semiconductor devices.
EMI can affect an electrical circuit by, among other ways, causing electromagnetic induction, electrostatic coupling and/or conduction. Such disturbances may degrade the performance of the electrical circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data, for example, from the effects of ultraviolet rays. An unshielded semiconductor device will tend to act as a detector for EMI (for example, radio signals) commonly found in the domestic environment. Light emitting diode (LED) lighting, for example, is a known source of EMI. Therefore, it is desirable to prevent, to an acceptable degree, the effects of ambient light that can alter the electrical characteristics of such light sensitive devices.
Conventionally, EMI shielding of semiconductor devices uses metal or polymer casings with a thin metal layer applied to the inside of the casing and affixed to a printed circuit board (PCB) to resolve EMI issues. This type of PCB-level shielding encapsulates the entire semiconductor device.
There are, however, semiconductor devices in combination with photonic components, which still require selective exposure to ambient light. Thin film photoelectric conversion devices are integrated with other semiconductor devices, which must be shielded from the ambient light. A new generation of electronic devices can be powered by energy harvesters such as photovoltaics, for example, self-sufficient wrist watches to wireless sensors that obtain power from the environment they are placed in. Other electronic devices, for example, ambient light sensors that control the display luminosity of mobile phones depending on ambient brightness and wearable devices such as smart goggles or smart contact lenses that project a miniature display of information in front of your eyes.
As such, PCB-level shielding will not meet the requirements of semiconductor devices with photonic components as the photonic components still require selective exposure to ambient light to function.